Inductor-type furnace



g- 12, 1930- 7 E. F. NORTHRUP 1,772,579

INDUCTOR TYPE FURNACE o riginal Filed Feb. 14, 1925 Patented Aug. 12, 1930 UNITED STATES PATENT OFFICE EDWIN FITCH NORTHRUP, OF PRINCETON, NEW JERSEY, ASSIGNOR TO AJAX ELECTRO- THERMIC CORPORATION, OF TRENTON, NEW JERSEY, A CORPORATION OF NEW JERSEY INDUCTOR-TYPE FURNACE Original application filed February 14, 1925, Serial No. 9,312. Divided and this application filed December 7, 1928. Serial No. 324,396.

My invention relates to electric furnaces of the coreless inductor type.

A purpose of my invention is to use edgewise windings in multiple to secure maximum cooling for a turn ol conductor having considerable extent parallel to the axis of the coil.

A further purpose is to make it possible to cover a desired belt for the entire crucible of a furnace by a comparatively small number of turns of conductor which may then be given a large amperage.

Further purposes will appear in the specification and in the claims.

I have preferred to illustrate my invention by two slight modifications of a single-main form only, selecting the form shown by rcason of its value in illustrating the principles of the invention.

Figure 1 is a diagrammatic view illustrating one of the connections in which my furnace may be applied.

Figure 2 is a fragmentary section showing preferred cdge-wound inductor structure with multiple path water cooling.

Figure 3 is a corresponding section show ing air-cooled edgewise wound coils.v

Figure 4 is adiagrannnaticview of an inductor having automatic adjustment of'primary current flow to depth of charge.

In the drawin s similar numerals indicate like parts.

My invention embodied herein was disclosed in my application for patent for induction electric furnace, filed February 14, 1925, Serial Number 9,312, co-pending herewith, of which application this is a division.

In Figure 1 a capacity C is placed across the line in pa 111101 with the furnace coil 7 which is supplied with current from the generator G, the load resistance being separately indicated at r. The current in the line from the generator will be substantially in phase with the generator voltage.

Because of the desirability in large furnaces of having a small munbcr of turns with a considerable vertical space occupied by the turns and the necessity for a high rate of heat withdrawal from the inductor, I have illustrated in Figure Zboth the edgewisc winding and the water-cooling which is so desirable where the rate of heat withdrawal must be a maximum. I have also included in this figure the multiple grouping of edgewise wound conductors by which a turn, in cross section extending over a distance parallel to the axis greater than its radial depth may still be edgewound and water-cooled. These features lit in with the multiple flow of cooling fluid applied by me in other furnaces.

In Figure 2 the individual conductors 15' or 15 (which may be air or water-cooled) are edgewound and are shown as water-cooled. In the fragmentary Figure 3 these conductors are shown as edgewound solid and air-cooled.

Both the water-cooled and air-cooled conductors are shown as connected in multiple, the unit of multiple shown being three, so

that each set of three conductors is electrically connected in multiple to comprise one turn, the diagrammatic connections being shown at 10 and 10. The cooling water is supplied through insulating tubes to inlets 11 and is vented to discharge at 12, the several inlets and discharges being not connected turn by turn in the illustration but obviously being adapted to have as many inlets and as many outlets, electrical and fluid, for the entire coil as may be preferred.

Because the individual conductors are grouped in sets the conductors of each set require no insulation from each other, greatly increasing the unit volume of copper per unit length axially of the inductor space; but the turns, comprising a number of conductors each, are insulated from each other as at 13. Air cooling space is shown at 14 and a heat insulating and electrical insulating lining 8 is placed between the coil and the cruicible, preferably against the coil.

In Figure 4 I show automatic regulating mechanism for adjusting the input of electric energy proportionally to the axial extent of the charge, which in the case of a, crucible becomes the depth of charge.

The supply to the coils is compensated for power factor correction as in Figure 1 by condensers C.

In this figure the inductor coil is divided into a plurality of sections shown in the illustration as two; these sections of inductor being connected in multiple with the current supply and, if water cooled, also preferably with multiple water passages and the usual tube insulation from the connecting pipes. Obviously the number of such sections electrically in multiple can be increased without varying from the theory of my invention though necessarily with practical limits as to the expediency.

The inductor coil sections 7 and 7 which are in parallel will operate precisely as the series coil when on full charge, except that their parallel connection will correspondingly increase the current flow. However, the current flow in each section is limited by the impedance of the section, and there will be a very much reduced impedance within the section when it surrounds a conducting charge. As a result with a depth of charge equal to half the furnace depth the impedance of the lower coil 7 2 would be substantially reduced by reason of the charge whereas the reactance of the upper coil 7 would remain a maximum. There would result from this a natural automatic adjustment of the current by which a relatively small current only fit) would fiow through the coil 7, ;whereas the coil 7 would take a large current.

The current is thus automatically much restricted to the portion of the coil surrounding the charge, greatly improving the coupling and reducing the 2' 1" inductor loss. At the same time the power factor will be improved and the efficiency will be increased.

Subject to requirements of simplicity and strength the conditions of intended use as they affect the depth of furnace charge must be considered largely in determining the number and size of sections of sub-divisions of the inductor coil in each given case.

It will be evident that the water-cooled and air-cooled forms both present the advantage of individual edgewise winding at the same time that the cross-section of the turn covers a considerable furnace length; also that even without insulation between the separate conductors the passage of eddy currents between the conductors will be substantially elim inated.

It will be further evident that the use of multiple conductors per turn can be applied equally well to inductors having the entire length of the inductor in series as in Figure 1, or to inductors having a plurality of inductor sections in parallel of which two sec- -ions are shown in Figure 4:.

It will be further evident that other forms of power factor correction could be used than that shown in Figure 1.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain part or all of the benefits of my invention without copying the structure shown,

and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is 1. In an induction electric heating device, an inductor coil having each efi'ective turn made up of a plurality of water-cooled conductors electrically in multiple.

2. In an induction electric heating device, an inductor coil having each effective turn made up of a plurality of edgewise-wound conductors electrically in multiple.

3. In an induction electric heating device, an inductor coil having more than one turn, edgewise wound and having a turn extent axially equal to or greater than the radial depth of the edgewise winding.

4.. A coreless furnace inductor comprising a plurality of coil parts electrically in parallel and adapted to surround the same charge.

5. A coreless furnace inductor comprising a plurality of coil parts electrically in parallel and adapted to surround the same charge, and power factor correction across the lineof current supply to the parallel coil parts.

EDWIN FITCH NORTHRUP. 

